The former Fine Gael Senator, Liam Cosgrave, has pleaded guilty at the Dublin Circuit Criminal Court to making a false or misleading report of a political donation.
Cosgrave failed to declare that he received a single donation exceeding £500 or donations from the same person with an aggregate value of £500 between 15 May and 31 December 1997.
The 49-year-old could face up to three years in prison and/or a fine of more than €25,000.
He admitted at the Flood Tribunal last year, that he failed to declare what he described as a legitimate political donation of more than €3,000 from lobbyist Frank Dunlop.
Cosgrave is a former Fine Gael TD and Senator who comes from a long and distinguished political dynasty.
He is the son of former Taoiseach, Liam Cosgrave, and grandson of William T Cosgrave who was President of the Executive Council of the Irish Free State from 1922 to 1932.
Following an investigation by the National Bureau of Criminal Investigation, Cosgrave originally faced two charges but today the State only proceeded with one of them to which he pleaded guilty.
Sentencing was adjourned until February next year.